DUBLIN — The cost to replace the Charcoal Road bridge — a residential neighborhood that includes the Dublin Lake Club — is expected to cost $480,000 more than expected at $1.18 million. The project is to be 80 percent state-funded, with 20 percent paid for by the town.

The town’s share of the cost is an estimated $236,000, part of which voters have already approved. An additional $126,000 will have to be raised through a warrant article at Town Meeting 2014.

The condition of the soils under the existing 18-foot span bridge, which was built in 1976, are soft and have greatly contributed to the bridge’s deterioration over time, said Select Board member Sterling Abram at Tuesday evening’s public hearing, where preliminary designs for a new bridge were discussed. “The existing wing walls are shifting and tipping,” Abram said of the walls that help support the structure.

Several years ago, the Select Board, at the direction of the N.H. Department of Transportation, limited bridge crossings to a weight of 10 tons because of the deterioration. But it wasn’t until later engineering studies, Abram said, that the source of the deterioration became more apparent.

The most recent proposal for a new bridge takes into account the poor soil conditions on the banks of Charcoal Brook and surrounding wetlands, with engineers having designed a more complex transportation system, said Shannon Beaumont of Manchester-based CLD Consulting Engineers at Tuesday’s meeting.

But that higher-tech design does come at a high cost, town officials said.

“It is going to cost us a lot more than anyone anticipated,” Abram told the Ledger-Transcript after Tuesday’s presentation, explaining that the town didn’t anticipate exceeding the $700,000 mark.

During the public hearing, Abram told residents, “I feel like we exhausted every possibility there was to drive costs down and keep the design streamlined and efficient.”

The bridge is inspected by the DOT each year. The last inspection was a few months ago, Abram said, adding that based on those results there is no immediate need to close the bridge.

Bridge construction is slated for fiscal year 2015, meaning that construction could start as early as July 2014, said Beaumont. She said the bridge will be closed for a couple of months during construction, which will likely take place in the summer months. For residents and emergency personnel, this may mean taking a circuitous route home or to the scene of an accident or fire.

In 2010, voters approved $110,000 for design and engineer work for bridge replacement at Charcoal Brook on Charcoal Road with $74,000 coming from the bridge repair/replacement capital reserve fund. The money raised in 2010 will help cover the town’s 20 percent, or approximately $236,000, towards the project. Voters will get a chance to weigh in on funding for bridge construction in a warrant article at a later date, Abram said.

Alyssa Dandrea can be reached at 924-7172 ext. 228 or adandrea@ledgertranscript.com. She’s on Twitter at @alyssadandrea.